Do technology externalities justify restrictions on emission permit trading?

International emission trading is an important flexibility mechanism, but its use has been often restricted on the ground that access to international carbon credits can undermine the domestic abatement effort reducing the incentive to innovate and, eventually, lowering the pace of climate policy-induced technological change. This paper examines the economics that is behind these concerns by studying how a cap to the trade of carbon offsets influences innovation, technological change, and welfare. By using a standard game of abatement and R&D, we investigate the main mechanisms that shape these relationships. We also use a numerical integrated assessment model that features environmental and technology externalities to quantify how limits to the volume, the timing, and the regional allocation of carbon offsets affect climate policy costs and the incentive to invest in innovation and low-carbon technologies.